You didn't have a gap in your HSA history so no worries.
You can also take the distribution from the new HSA or the old, it doesn't matter. And you can rollover the remaining $50 from the old account into the new account if you like. What matters is that you had an HSA open and available, it doesn't have to be the same account every time.
If you make payroll contributions, your tax savings will be slightly higher, since payroll contributions are exempt from social security and medicare tax as well as income tax. But it would take all year to fill up the account instead of doing a lump sum.
